Power supply for a laser

ABSTRACT

An improved gas laser is disclosed. The laser has a support tube to support and to maintain the alignment of the optical resonator structure. The gas lasing medium is used within the support tube to maintain the tube at a substantially constant temperature above the ambient. Furthermore, an active temperature controller is disclosed. The temperature controller maintains the gas lasing medium in the support tube at a substantially constant temperature. An active pressure controller is also disclosed. The active pressure controller uses a pressure sensor, an electronic processor, and a motor-driven needle valve to maintain the pressure of the gas lasing medium in the laser within the desired operating pressure range. The laser can also be switched in operation from a continuous mode to a pulsing mode. An active power control system is disclosed wherein the power output of the laser, through an active feedback loop is maintained at the desired level. Because the optical resonator structure is light weight, it can be mounted on a mechanical assembly. The beam is delivered to a desired location by the mechanical assembly. Finally, a distributive lasing system comprising a centralized pump delivering the lasing medium to a plurality of remotely located optical resonator structures is disclosed.

TECHNICAL FIELD

The present invention relates to an improved laser, and/or componentsthereof. More particularly, the present invention relates to an improvedCO₂ laser and components thereof.

BACKGROUND OF THE INVENTION

A laser has many components. Because a laser is a precision instrument,many of these components must be of high precision. One such componentis the optical resonator structure. The optical resonator structure hasa cavity in which the active lasing medium is excited to produce thebeam of coherent radiation. At one end of the optical resonator cavityis a first highly polished mirror, which is nearly one hundred percent(100%) reflective; a second highly polished mirror is at the other end,which is less reflective than the first mirror and permits some of theradiation to be transmitted therethrough. Coherent radiation generatedwithin the optical resonator cavity is reflected from the first mirrorto the second mirror until sufficient amount of energy of coherentradiation is generated and is transmitted through the second mirror.

Because the optical resonator structure must be aligned such thatphotons of radiation reflected from one mirror is incident on the othermirror, the structure must be extremely precisely aligned. Anymisalignment can cause the laser to produce a reduced output or even tofail to generate a beam of laser radiation. The optical resonatorstructure must be precisely aligned, even when it is subjected tovariation in alignment and position due to variations in the ambienttemperature. In addition, heat generated within the optical resonatorcavity caused by the excitation of the lasing medium can cause theoptical resonator structure to become misaligned or mispositioned.

In the prior art, it is known to use a stablizing fluid, such as wateror oil, which is heated to a fixed temperature and passed into theoptical resonator structure to maintain the structure at a fixedtemperature. This, however, requires the use of a fluid which isdifferent from the lasing medium, thereby necessitating another set ofplumbing fixtures and the like. In addition, the temperature of thestablizing medium is generally maintained by a simple thermostaticheater. To our knowledge, there has never been a laser using atemperature stablizing lasing medium whose temperature is activelycontrolled. By active control, it is meant that the temperature issensed, is compared to a fixed reference, and in response to thecomparison, the temperature of the fluid is changed, all of which isdone in a closed loop feedback control configuration.

Another component of a laser is the power-supply. The power supplygenerally comprises a plurality of lines (usually three) connected to athree-phase power source. These plurality of lines are connected to aset of primary coils (also usually three), which are wound about atransformer. A plurality of secondary coils (also usually three) arealso wound about the transformer. The transformer increases the voltageof the secondary coil from the primary coils. In the prior art, tocontrol the mode of operation of the laser from continuous to pulsing,usually a control device, such as a vacuum tube, is used. Since a vacuumtube runs on DC voltage, and since the power supplied to the primarycoils is AC in nature, the vacuum tube is placed in the circuit afterthe secondary coils. Since the secondary coils receive an increasedvoltage from the transformer (usually on the order of tens of thousandsof volts), the vacuum tube must be suitable for such high voltageapplication. Necessarily, these tubes are expensive.

To our knowledge, in the prior art, there has not been any system tocontrol the power output of a laser in response to the desired level ofpower output. In addition, to our knowledge, there is no laser systemhaving an active pressure control loop to control the pressure of thegas lasing medium.

In September of 1982 at the International Machine Tool Show in Chicago,Ill., a system was disclosed wherein a fixed laser generated a fixedbeam of coherent radiation. A robot having an articulated arm moved awork piece in and out of the beam of coherent radiation to effectuatevarious cutting and scribing actions onto the work piece as a result ofthe relative movement of the fixed beam of coherent radiation and themovable work piece. In the medical area, a laser generating a beam ofcoherent radiation has been delivered to a desired location by passingthe beam of coherent radiation through an articulated arm wherein themovement of the articulated arm moves the beam. However, to ourknowledge, in the prior art, there has not been any industrial system todeliver a beam of coherent radiation to a desired location by amechanical assembly which comprises a plurality of coupled structuralmembers in one of which the laser is located. The movement of theassembly moves the laser and the beam to deliver the beam to the desiredlocation. Finally, to our knowledge, there is no prior art relating to adistributive lasing system wherein a centralized pump and power supplydelivers the electrical power and the active gas lasing medium to aplurality of remotely located optical resonator structures to activatethe lasing action.

SUMMARY OF THE INVENTION

In the present invention, a gas laser which is operable in a continuousor pulsing mode is disclosed. The gas laser comprises a gas lasingmedium and a gas discharge tube enclosing the medium. The gas dischargetube is positioned within an optical resonator structure. Means forexciting the gas lasing medium in the discharge tube is provided. Saidmeans comprises three leads for connecting to a three-phase powersource. A plurality of primary coils are connected to the leads. Aplurality of secondary coils are connected to diodes to provide power tothe electrodes located in the gas discharge tube. A transformer meansincreases the voltage of the power source to the secondary coils. Meansfor changing the magnetic flux flow pattern in the transformer meansfrom a symmetric flux pattern to an asymmetric flux pattern is alsoprovided, whereby the symmetric flux pattern causes the gas laser tooperate in a continuous mode and whereas the asymmetric flux patterncauses the laser to operate in a pulsing mode.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic overall view of an improved laser, incorporatingthe present invention.

FIG. 2a is an enlarged view of the optical resonator structure of FIG.1.

FIG. 2b is a cross-sectional view taken along the line b--b of FIG. 2a.

FIG. 3 is a circuit diagram of an active temperature controller.

FIG. 4(a-c) are various waveforms representing the signals at variouslocations of the circuit shown in FIG. 3.

FIG. 5 is a schematic circuit diagram of the power supply used in thelaser of FIG. 1.

FIG. 6 is a schematic circuit diagram of a type of switch suitable foruse in the power supply shown in FIG. 5.

FIG. 7 is a side view of the mechanical coupling of a motor and a needlevalve used in a pressure regulator for the laser of FIG. 1.

FIG. 8 is a schematic circuit diagram of the active pressure controllerfor controlling the pressure of the gas in the laser shown in FIG. 1.

FIG. 9(a-c) are timing diagrams for various components of the circuitshown in FIG. 8.

FIG. 10 is a schematic circuit diagram of a power control system used inthe laser in FIG. 1.

FIG. 11 is a perspective view of a laser beam delivery apparatus.

FIG. 12 is a perspective view of another laser beam delivery apparatus.

FIG. 13 is a perspective view of yet another laser beam deliveryapparatus.

FIG. 14 is a side view of still yet another laser beam deliveryapparatus.

FIG. 15 is a block diagram of an apparatus for interchanging a componentof the laser beam delivery apparatus.

FIG. 16a-b are schematic block diagrams of laser distributive systemshaving a plurality of optical resonator structures and a centralizedpump and power supply.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown an overall view of an improved laser10. Although the discussions set forth hereinafter will relate to a CO₂type of laser, it should be apparent that the invention is not solimited. In particular, the invention can be used in any type of laserhaving a fluid lasing medium.

The gas laser 10 comprises a gas inlet 12 for introducing the gas lasingmedium into the laser 10. In a CO₂ type laser, the gas is a mixture ofCO₂, N₂ and He, although the active lasing medium is the CO₂ gas. Thegas is introduced into the inlet 12 and passes through a motor-drivenneedle valve 14 for controlling the flow of the gas passing through theneedle valve 14. This will be explained in greater detail hereinafter.The gas is then combined with recycled gas from the recirculated pipe 16and is introduced into a first heat exchanger 18. A cooling fluid, suchas water, is also introduced into the first heat exchanger 18 to coolthe temperature of the gas. From the first heat exchanger 18, the gas ispassed across a temperature sensor 20, which supplies a signal to atemperature control processor 22 which will also be explainedhereinafter. From the temperature sensor 20, the gas is introduced intothe optical resonator structure 24.

Within the optical resonator structure 24, the gas is passed into adischarge tube 26. Within the gas discharge tube 26 the lasing action ofthe gas is produced, generating a beam 28 of coherent radiation. Fromthe discharge tube 26, the gas is then supplied to an exhaust tube 27.The gas is then passed through a pressure sensor 30 which, with thepressure controller 32, controls the pressure of the gas within thelaser 10. After passing through the pressure sensor 30, the gas passesthrough a second heat exchanger 34. The gas is then pumped by a pump 36and is recycled along with the new gas from the gas inlet 12. The pump36 is a positive displacement "Roots" type pump. A small vacuum pump 35of the rotating vane type maintains the gas mixture at about 60 torr, bycontinually drawing off a small amount of gas through an orifice 37.

OPTICAL RESONATOR STRUCTURE

Referring to FIG. 2a, there is shown the optical resonator structure 24in greater detail. The optical resonator structure 24 comprises asupport tube 40, into which the gas lasing medium is first introduced.The gas flow is indicated generally by the arrow. The support tube 40aligns and supports the optical resonator structure 24 with a firstmirror 42 positioned on a first end bracket 41 at one end of the supporttube 40 and a second mirror 44 positioned on a second end bracket 43 atthe other end of the support tube 40. The support tube 40 is attached toeach end bracket 41 and 43, and is positioned substantially parallel tothe discharge tube 26. Gas from the support tube 40 is passed to thedischarge tube 26 substantially near the ends of the support tube 40 andof the discharge tube 26 in a radial direction from the support tube 40to the discharge tube 26. Once the gas is introduced into the dischargetube 26, they then flow axially away from the ends of the discharge tube26. Away from the ends of the discharge tube 26, the gas from thedischarge tube 26 is passed to the exhaust tube 28.

As shown in FIG. 2b, there are two discharge tubes 26 in communicationwith the support tube 40 and the exhaust tube 27. Any number ofdischarge tubes 26 can be placed parallel to the support tube 40 and incommunication therewith. However, preferably, the discharge tubes 26 arepositioned axially spaced from one another by approximately 90 degrees.Also preferably for structural support, the support tube 40 should bepositioned substantially near the center of the optical resonatorstructure 24 to achieve the greatest stability and alignment.

In order to achieve the greatest stability and support for the opticalresonator structure 24, gas within the support tube 40 is maintained ata substantially constant temperature. Furthermore, preferably, thetemperature of the gas within the support tube 40 is maintained abovethe ambient temperature.

With the gas in the support tube 40 maintained at a constanttemperature, the stability of the optical resonator structure 24 and thealignment of the first and second mirrors 42 and 44 and the foldingmirrors 5 (only one is shown) are less likely to be affected bytemperature variations in the ambient or in the structure 24 caused bythe excitation of the gas in the discharge tube 26.

Within the discharge tube 26 are a plurality of anodes 62 and cathodes64. The anodes 62 and cathodes 64 are preferably spaced approximately16.5 inches apart. The discharge tube 26 is preferably 74 inches inlength, thereby accommodating four (4) anode-cathode sections. The outerdiameter of the discharge tube is preferably 51/4" with an innerdiameter of 41/2". The anodes 62 are positioned substantially near theends of the discharge tube 26 and near the gas inlet from the supporttube 40. The cathodes 64 are positioned away from the ends of thedischarge tube 26 near the gas exhaust from the discharge tube 26 to theexhaust tube 27. In the event more than one discharge tube 26 is used,the folding mirrors 5 or deflecting mirrors are used to provideincreased output power.

To provide overall physical stability, the optical resonator structure24 is made out of rigid cast aluminum. As a result, the structure 24 isof light weight. The end brackets 41 and 43 are kinematically mounted onsupport member 39. The support member 39 is generally parallel with thesupport tube 40 and with the discharge tubes 26 and the exhaust tube 27.The first end bracket 41 is rigidly fastened onto the support member 39.A mounting bolt 45 bolts the first end bracket 41 to the structuralmember 39. The bolt 45 is fastened such that it prevents any movement ofthe end bracket 41 in any direction. The second end bracket 43 has aslot 47 therein. A slot 47 is located on each side of the second endbracket 43 (only one is shown in FIG. 2a). The slot 47 is generally inthe x direction (as shown in the direction diagram of FIG. 2a). Amounting bolt 49 on the structural member 39 is passed through the slot47. The bolts 49 passing through the slot 47 permit the second endbracket 43 to move in the x and y directions. The bolts 49 prevent thesecond end bracket 43 from moving in the z direction. Substantially nearthe center of the second end bracket 43 is a hole 53 through which analignment pin 51 passes (as shown in the cut-away section of FIG. 2a).The alignment pin 51, through the slot 53, prevents the second endbracket 43 from moving in the y direction. The overall effect of thebolts 49 and the alignment pin 51 is to permit the second end bracket 43to move only in the x direction. Thus, when there is thermal expansionof the optical resonator structure 24, due to increase in temperature,the support tube 40 moves the first and second end brackets 41 and 43relative to one another only in the x direction. The movement of thefirst and second mirrors 42 and 44 in the x direction, which isgenerally parallel to the axial direction of the discharge tube 26,maintains the alignment of the mirrors for the photons to reflect fromone mirror to the other.

TEMPERATURE CONTROLLER

To maintain the temperature of the gas within the support tube 40, atemperature controller is provided. The temperature controller comprisesa temperature sensor 20, an electronic processor 22, and a solenoid 50for controlling the flow of the water into the first heat exchanger 18to cool the gas.

Referring to FIG. 3, there is shown a schematic circuit diagram of thetemperature control processor 22. The temperature sensor 20 measures thetemperature of the gas and produces a first signal in response thereto.The temperature sensor 20 is an industry component designated as LM334.A portion of the temperature processor 22 comprises a circuit known as a"dither" 52. The dither 52 produces a saw-tooth waveform which variesapproximately every 30 seconds. This is shown in FIG. 4a. The saw-toothsignal from the dither 52 and the first signal from the temperaturesensor 20, which is a DC signal, are combined at a summing junction 54.The summing junction 54 simply adds the two signals together. An exampleof the waveform at the junction 54 is illustrated in FIG. 4b. Thecombined signal from the summing junction 54 is supplied to anoperational amplifier 56, which merely isolates the signal from the restof the system.

From the operational amplifier 56, the summed signal is supplied to acomparator 58. The comparator 58 is an industry part LM723. It has aninternal reference voltage and an outside potentiometer can be attachedto the internal voltage reference to adjust it. The outsidepotentiometer can adjust the internal voltage to a level which isrepresentative of a reference temperature. The comparator 58 comparesthe summed signal to the reference signal to produce a drive signal. Thecomparator 58 compares the two signals by subtracting the referencesignal from the summed signal. An example of the waveform from thecomparator 58 is shown in FIG. 4c. The drive signal is then supplied tothe solenoid 50 through an optical SCR switch 62. The optical SCR switchis a component D2402 made by I. R. Crydom.

The drive signal from the comparator 58 which is supplied to thesolenoid 50 is a DC signal with a saw-tooth signal superimposed thereon.The saw-tooth signal turns on the solenoid approximately every 30seconds. The length of the "on" period is determined by the DC level.Thus, if the drive signal from the comparator 58 were small, thesolenoid 50 would nevertheless be turned on every 30 seconds for amomentary period of time. An example of this is shown in FIG. 4c. Byhaving the solenoid 50 activate at a fixed rate but for a variableperiod of time, the temperature bandwidth is decreased.

In the prior art, a thermostat normally varies between two temperaturevalues: a first temperature and a second temperature. When thetemperature of the medium reaches a first temperature, the thermostatwill open to cool it. When the temperature of the medium reaches asecond temperature, the thermostat will close to prevent furthercooling. The switch between the two temperature values is of constantamplitude. Only the amount of time during which the switching operationis performed is varied.

In contrast, in the temperature control processor 22, the solenoid 50 isforced to switch at a constant rate, but at a variable pulse width,thereby decreasing the temperature amplitude. This reduces the variationbetween the first temperature and the second temperature; i.e., thetemperature at which the gas medium should be cooled and the temperatureat which the cooling process should be stopped. Thus, a more accuratetemperature controller is achieved.

In the preferred embodiment, the temperature of the gas is maintained ata level above the ambient. This avoids fluctuation of temperature of thegas caused by variation in temperature of the cooling fluid.

POWER SUPPLY SYSTEM

Referring to FIG. 2a, there is shown the gas discharge tube 26.Positioned within the gas discharge tube are a plurality of anodes 62and a plurality of cathodes 64. For a CO₂ laser, to cause the lasing ofthe gas medium within the gas discharge tube 26, a high voltage DCsource (typically on the order of tens of thousands of volts) must besupplied to the anodes 62 and cathodes 64.

Referring to FIG. 5, there is shown a schematic circuit diagram of apower supply system 68 for supplying high voltage DC power to theelectrodes 62 and 64 in the discharge tube 26. The power supply systemcomprises a first, a second and a third lead (φ_(A), φ_(B), φ_(C),respectively). The first lead φ_(A) is connected to a first saturablereactor 70. The second lead φ_(B) is connected to a second saturablereactor 72. The third lead φ_(C) is connected to a third saturablereactor 74. The leads φ_(A), φ_(B), and φ_(C) are connected to aplurality of primary coils 76, 78 and 80 of a transformer T₁. Threesecondary coils 82, 84 and 86 are also connected to the transformer T₁.The output of the secondary coils 82, 84 and 86 are connected through adiode bridge comprising a plurality of diodes to form the DC powersupply. This is the high voltage which is supplied to the electrodes 62and 64 within the discharge tube 26. The foregoing described prior artpower supply system 68, when connected to a three-phase power source(e.g. 480 volts A.C.) and the system 68 is in operation, will cause thegas laser 10 to operate in a continuous mode, i.e., the beam 28 ofcoherent radiation produced from the discharge tube 26 is generatedcontinuously.

We have found that, by simply adding a switch, for example 90a, whichconnects between any of the two leads, for example, φ_(B) and φ_(C), ora switch, for example 90b, in one of the leads, for example, φ_(C), fromthe primary coils to the power source, will cause a change in the fluxpattern in the transformer T₁. More particularly, the change in the fluxpattern results in an asymmetrical flux flow in the transformer T₁. Theresult of an asymmetrical flux pattern in the transformer T₁ is thatwhen the power supply system 68 is connected to the electrodes 62 and 64in the discharge tube 26, the laser 10 will operate in a pulsing mode.In the event the leads φ_(A), φ_(B) and φ_(C) were connected to a 60 Hzthree-phase power source, and either switch 90a is introduced shortingthe leads φ_(B) and φ_(C), or switch 90b is added opening the lead φ_(C), a pulsing rate of 120 HZ is observed.

The switch 90a or 90b can be an optical SCR switch, such as the D2402from I. R. Crydom, as previously described. The schematic circuit forsuch a switch is shown in FIG. 6.

ACTIVE PRESSURE CONTROLLER

The active pressure controller for the laser 10 comprises a pressuresensor 30, a pressure control processer 32 and a motor driven valve 14.This is shown in FIG. 8. The pressure of the gas in the laser 10 iscrucial in order to maintain the proper output of the gas discharge tube26. Also, the vacuum pump 35 pumping through a small orifice 37, iscontinually draining the laser 10 of a small percentage of its gas load.This leakrate is replenished through the motor driven valve 14.

The sensor 30 is a solid state, temperature compensated pressuretransducer. The preferred embodiment of the pressure sensor is a142PC15A, commercially available from Microswitch/Honeywell. Thepressure transducer 30 generates a first voltage signal which isproportional to the pressure of the gas. The output of the transducer 30increases monotonically with the absolute pressure.

The first signal from the pressure sensor 30 is supplied to a firstoperational amplifier 92 (shown in the upper right hand portion of thefirst LM324). The first operational amplifier 92 is a DC comparatorwhose output is proportional to the error difference between pressuretransducer output voltage (from the sensor 30) and pressure referencelevel setpoint (from the first adjustable potentiometer 94). A summingjunction 96 follows the first operational amplifier 92. The firstoperational amplifier 92 supplies the summing junction 96 with thesignal necessary to maintain DC pressure level during normal long termoperation.

A second potentiometer 98 is directly connected to the gear train of themotor and gas flow valve 14. The second potentiometer 98 is driven by aDC level and the output of the second potentiometer provides a signalproportional to the valve opening. A second operational amplifier 100 isconnected in parallel with the first operational amplifier 92 andtranslates the second potentiometer 98 output signal into a secondsignal proportional to rate of change of inlet gas flowrate. Thisprovides a velocity feedback signal to the summing junction 96 that isnecessary for stable operation.

A third operational amplifier 93 provides as its output a voltageproportional to the position of the second potentiometer 98 andtherefore of the gas flow control valve. A fourth operational amplifier95 also provides a voltage proportional to position of the secondpotentiometer 98 and therefore of the gas flow control valve. These twooperational amplifiers 93 and 95, when provided with proper high and lowlimit reference values will supply a signal to the summing junction 96necessary to restrict the needle valve excursion and keep the valve fromjamming onto the stop or from excessive flow rate during startup. Thethird operational amplifier 93 prevents excessive flow rate while thefourth operational amplifier 95 prevents jamming.

A fifth operational amplifier 97 is a driver for the output transistors(shown as 2N3439 and 2N5416). These transistors are connected in aconfiguration commonly known as a totem-pole configuration. The motor 14is connected to the center of the totem-pole in order to receive properdrive of either positive or negative polarity necessary to drive thevalve clockwise or counter-clockwise, thereby closing or opening thevalve in response to the voltage present at the summing junction 96.

The motor and valve 14 assembly comprises an ETI/Polaris IndustrialEnterprise motor assembly, consisting of a DC motor, the secondpotentiometer 98 and a reduction gear. The motor 104 rotates the shaft106. Attached to the shaft 106 is a reduction gear 108. The reductiongear 108 is coupled to another gear 110 which is attached to the shaft112 of a flow tube 114. The flow tube 114 has a needle valve therein(not shown) and in response to the rotation of the shaft 106 of themotor 104, the shaft 112 of the flow tube is rotated which moves theneedle valve, thereby controlling the pressure of the gas passingthrough the flow tube 114. The preferred embodiment of the flow tube 114is commercially available as B-125-60 manufactured by Porter InstrumentCompany.

In normal steady-state operation, the high limit and the low limitoperational amplifiers 93 and 95 respectively provide no signal to thesumming junction 96. The summing junction 96 therefore combines thepressure transducer feedback, the setpoint reference level, and the gasflowrate rate of change. This combined signal is compared against zeroby the fifth operational amplifier 97. Any offset from zero, eitherpositive or negative is supplied to the motor 104 as a DC drive levelproportional to the offset from zero. The gas flowrate into the laser 10is therefore actively controlled so as to maintain gas pressuredeveloped in the laser 10 at a constant and selected level.

The four additional operational amplifiers shown on the schematic areused to trip three pressure level setpoints used for various startupsignals and to provide stiff voltage references to the pressure controlprocessor. The voltage reference could be derived elsewhere. Thereforethese four operational amplifiers are not required for proper operationof the pressure control processor.

POWER CONTROL SYSTEM

Referring to FIG. 10, there is shown a schematic block circuit diagramof a power control system 120 used in the laser 10. A percentage of theintercavity power of the laser 10, a beam of coherent electromagneticradiation, is detected by a power meter 122. The power meter 122generates a voltage signal which is proportional to the output radiantenergy of the laser 10. This power signal is supplied to a firstoperational amplifier 124 which serves merely to buffer the power signalfrom the rest of the system 120. The power signal is then passed to afirst comparator 126.

A switch 128 has a plurality of settings which the operator can set tothe desired power level for the laser 10. A programmable read onlymemory 130 generates a digital signal in response to the address settingderived from the switch 128. The digital signal is then passed to a DCreference 132 which decodes the value from the PROM 130 and generates alevel signal. The level signal from the DC reference 132 is thenbuffered by amplifier 134. A signal which is representative of thetemperature of the ambient is also supplied to the amplifier 134. Thesignal from the DC reference 132 is supplied to the "+" input of theamplifier 134, while the signal representative of temperature issupplied to the "-" input of the amplifier 134. The signalrepresentative of temperature can be derived from any source, such as athermistor. The compensated signal is then passed to the firstcomparator 126. The first comparator 126 is an operational amplifierwith the signal from the amplifier 134 being supplied to the "+" inputand with the power signal from the power meter 122 being supplied to the"-" of the input. The output of the first operational amplifier 126 isthen used to control a reactor drive 136. The reactor drive 136 controlsthe first, second and third saturable control coils 70, 72, and 74,respetively, as shown and discussed in FIG. 5. By controlling thesaturable control coils 70, 72 and 74, the high voltage supply system 68is thereby controlled. The power level of the high voltage system 68, inturn, controls the degree of discharge current which occurs within thedischarge tube 26.

It will be appreciated that, with the power control system 120, activecontrol of the power of the output of laser 10 is achieved. Furthermore,direct power setting of the laser 10 with feedback control has also beenaccomplished.

LASER BEAM DELIVERY APPARATUS

Referring to FIG. 11, there is shown a laser beam delivery apparatus140. As previously described, the laser 10 comprises an opticalresonator structure 24 which can be of extremely light weight. Thus, theoptical resonator structure 24 can be mounted away from the pumps, heatexchangers, etc. In the laser beam delivery apparatus 140 shown in FIG.11, the optical resonator structure 24 is shown as producing a beam ofcoherent radiation 28. A mechanical assembly 155 is also shown. Themechanical assembly 155 comprises a plurality of coupled structuralmembers. A first structural member 142 is linked to a second structuralmember 144 which is linked to a third structural member 148, etc. Ateach of the linkage of the structural members is a joint, shown forexample, as 146 or 150. Within each joint is a mirror. The structuralmembers are preferably of hollow, cylindrical tubes. The beam 28 isaligned to pass substantially through the center of the cylindricalmember, to impinge the mirror positioned in the joint. The relativemovements of the structural members forming the joint moves the mirror.Thus, the beam 28 can be delivered to the desired location by moving thestructural members relative to one another such that the beam 28reflected from the mirror in the joint will then impinge on the desiredlocation.

More specifically, in FIG. 11, the beam 28 is aligned to passsubstantially near the center of the axis of the cylinder of the firststructural member 142. The beam 28 is aligned to impinge the firstmirror 146 and to reflect therefrom. Beam 28 reflected from the firstmirror 146 is aligned to pass substantially through the center of theaxis of the second cylindrical structural member 144 and is aligned toimpinge a second mirror 150. Beam 28 is then reflected from the secondmirror 150 and is aligned to pass through the center of the cylinder ofthe third structural member 148, and is aligned to impinge a thirdmirror 152. The beam reflecting from the third mirror 152 is aligned topass through a telescopic member 154. At the end of the telescopicmember 154 is a fourth mirror 156 from which the beam 28 is reflected.The beam 28 is then passed through a focusing lens 158 and is thenfocused onto the desired location 160.

The entire mechanical assembly 155 is mounted on a frame 162 withmotor-driven belts 164 and 166, respectively. The motor-driven belts 164and 166 propel the mechanical assembly 155 with the optical resonatorstructure 24 in either the x or the y directions. The movement of themechanical assembly 155 in the x or y direction moves the beam 28 in thex and y directions. The telescopic member 154 delivers the beam 28 inthe z direction.

In the apparatus 140, shown in FIG. 11, the relative alignments of themirrors 146, 150, and 152 are set at the factory. The beam 28 is alignedto impinge the first, second and third mirrors 146, 150 and 152,respectively, and to be delivered down the center of the telescopicmember 154. In operation, only the entire assembly 155 is moved eitherin the x or y direction and the telescopic member 154 is moved in the zdirection. In addition, the telescopic member 154 can be rotated aboutthe z axis, while the focusing lens 158 can be rotated about the y axis.

Referring FIG. 12, there is shown another laser beam delivery apparatus170. This laser delivery apparatus 170 is similar to the laser deliveryapparatus 140. The apparatus 170 comprises an optical resonatorstructure 24 for generating a beam 28 of coherent radiation. Themechanical assembly 172 for delivering the beam of coherent radiationcomprises a first structural member 142, a second structural member 144,with a first joint 146 having a mirror therein, and a second joint 150having a mirror therein, all similar to that described for the apparatus140. The beam 28 from the resonator structure 24 is aligned to impingethe first mirror 146, to reflect therefrom and to impinge the secondmirror 150 and to reflect therefrom to impinge a movable focusing head174. The movable focusing head 174 comprises a third mirror 176 which isaligned to receive the beam 28 to reflect therefrom and to impinge afocusing lens 178.

The mechanical assembly 172 is mounted on a pair of guide rails 180 and182 respectively. The optical resonator structure 24, mounted on themechanical assembly 172 is movable in the Y direction. The movablefocusing head 174 is adapted to move along a third rail 184 in the Xdirection. The focusing action of the beam 28 by the focusing lens 178delivers the beam 28 in the Z direction.

Referring to FIG. 13 there is shown yet another laser beam deliveryapparatus 190. The laser beam delivery apparatus 190 comprises anoptical resonator structure 24 for generating a beam 28 of coherentradiation. A mechanical assembly 192 comprises a plurality of coupledstructural members, some of which are shown as 142, 144, 148 and 154,all as previously described. Each structural member is linked forrelative movement with another adjacent structural member therebyforming a plurality of joints. At each joint, a mirror is positioned toreceive the beam 28 and to reflect the beam 28 onto the next joint. Aplurality of such mirrors is shown as 146, 150, 152 etc. The mechanicalassembly 192 shown in FIG. 13 is capable of an innumerable degree ofmotion. The rotational degrees of freedom of each of those structuralmembers is shown by the arrows. The movement of the mechanical assembly192 moves the beam 28 and delivers a reflective beam, the beam 28 whichhas been reflected through the internal workings of the structuralmembers, through a focusing lens 194 to the desired location 196.

Referring to FIG. 14 there is shown yet another laser beam deliveryapparatus 250. The apparatus 250 comprises an optical resonatorstructure 24 mounted on a mechanical assembly 232. The mechanicalassembly 232 has a base 230. A first structural member 231 is rotatablymounted on the base 230. The resonator structure 24 is rotatably mountedon the first structural member 231. The beam 28 (not shown) from theresonator structure 24 is passed through an elastic joint 236 andimpinges a focusing head 238. The head 238 is rotatable about the point236. A focusing lens 240 focuses the beam 28 and delivers it to thedesire location.

Each of the foregoing describe the laser beam delivery apparatus, 140,170, 190 and 250 have been shown with only an optical resonatorstructure. Of course, as previously stated, the heat exchangers, thevacuum pump, and the power supply, all as previously described as beingnecessary for the operation of laser 10 must also be provided. For thelaser beam delivery apparatus 140, 170, 190 and 250, these otherportions are not shown but are connected to the optical resonatorstructure 24 through flexible coupling, and electrical connectors.

Each of the mirrors positioned in the joint formed by two adjacentstructural members of the mechanical assembly portion of the apparatus140, 170, 190 ro 250, can be a reflective means, of the type as shownand described in U.S. Pat. No. 4,379,622, which in addition toreflecting coherent beam impinging thereon also imparts a certain degreeof phase shift to that reflective beam. As shown and as described inU.S. Pat. No. 4,336,439, a circularly polarized beam, formed by alinearly polarized beam which is subsequently passed through a ninetydegree (90°) phase shifter has beneficial cutting and scribingproperties. Therefore, the reflective mirror can be a reflective mirrorwhich imparts a phase shift to the beam. The reflective mirror canimpart ninety degrees (90°), forty-five degrees (45°) or even zerodegree (0°) phase shift.

Since each laser beam delivery apparatus 140, 170, 190 and 250, alsocomprises a focusing head which focuses the beam 28 onto the desiredlocation, the focusing head, which comprises a focusing lens, determinesthe distance of focus from the head to the desired location. Referringto FIG. 15 there is shown an apparatus for changing the focusing head ofthe laser beam delivery apparatus. A laser beam delivery apparatus 140is shown with a laser focusing head 158. A plurality of interchangeablefocusing heads: 200, 202, 204 and 206 are positioned nearby. A secondmechanical assembly 155 having an arm and a grasp 208 is shown.Mechanical assembly 155 with the grasp 208 is capable of removing thefocusing head 158 from the laser beam delivery apparatus 140, andreplacing it with a focusing head of choice from the rack ofinterchangeable focusing heads 201. Therefore, by permitting theinterchangeability of the focusing head of the laser delivery apparatus140, greater flexibility is achieved.

DISTRIBUTIVE LASING SYSTEM

Referring to FIG. 16(a) there is shown a distributive lasing system 210.The distributive lasing system 210 is suitable for use in a factorywhere a plurality of optical resonator structures 24a, 24b, 24c etc. arein use in different locations of the factory. Each one of the opticalresonator structures 24(a-d) can be mounted on a mechanical assembly ofthe type as previously described. In the distributive lasing system 210shown in FIG. 16(a), a centralized gas pump 36 and heat exchanger 18 areshown. The lasing medium, the gas, is delivered from the central pump 36through the heat exchanger 18 to each one of the optical resonatorstructures 24(a-d), via pipes or hoses located throughout the factory.The gas is pumped from the centralized pump 36 and is heated by acentralized heat exchanger 18 and is passed on to a first opticalresonator structure 24(a), a second optical resonator structure 24(b), athird optical resonator structure 24(c) etc. The gas is then recycledback to the pump 36. A centralized power supply 212 supplies thenecessary electrical power to create the discharge within the dischargetube of each of the optical resonator structures 24(a-d). A backupvacuum pump 36' is shown as a pump to be used in the event of failure ofthe primary pump 36.

Referring to FIG. 16(b) there is shown another distributive lasingsystem 220. Similar to the distributive lasing system 210 shown in FIG.16(a), the distributive lasing system 220 shown in FIG. 16(b) comprisesa centralized pump 36. The pump 36 provides the active lasing medium toeach of the optical resonator structures 24(a-d). Again, the delivery ismade through pipes, hoses and the like. The gas is supplied to each ofthe optical resonator structures 24(a-d) and the exhaust gas from theoptical resonators structure is returned to the central pump 36.However, unlike the system 210 shown in FIG. 16(a), a heat exchanger18(a-d) is provided for heating the gas of the gas lasing medium to eachof the optical resonator structures 24(a-d). In this example, if thecentralized pump 36 were far away, a heat exchanger 18(a-d) should beplaced close to the respective optical resonator structure 24(a-d) inorder to minimize the heat loss from the transmission of the gas fromthe heat exchanger to the optical resonator structure. Similar to thesystem 210 shown in FIG. 16(a), a backup pump 36' is also shown. Ofcourse, in addition, a centralized power supply 212 would also beprovided.

The advantage of a distributive lasing system 210 or 220 is that nearthe work site all that is required would be the optical resonatorstructure 24. Since as previously described the optical resonatorstructure can be made lightweight and compact, the plumbing and theelectrical supply necessary to maintain the lasing action within theoptical resonator structure can all be centralized. This would result inelimination of duplication of vacuum pumps and power supplies. Inaddition, banks of vacuum pumps and of power supplies can be connectedin tandem to be switched on in the event of failure of one of thecomponents. From the foregoing description, it can be seen that thereare numerous advantages to a distributive lasing system as described.

We claim:
 1. In a gas laser of the type having a gas discharge tubecontaining a gas lasing medium, a power supply for operating said laserin a continuous mode, wherein said power supply having three leads forconnecting to a three phase power source, said leads being connected toa plurality of primary coils; a plurality of secondary coils; and atransformer means for increasing the voltage from the power sourcethrough the primary coils to the secondary coils, wherein theimprovement comprising:means for generating magnetic flux asymmetry insaid transformer means; whereby said magnetic flux asymmetry causes saidlaser to operate in a pulsing mode.
 2. The apparatus of claim 1, whereinsaid generating means comprises:switch means interposed between one ofsaid three leads and one of said primary coils for electricallydisconnecting said lead to said coil.
 3. The apparatus of claim 2,wherein said switch means is an optically driven SCR switch.
 4. Theapparatus of claim 1, wherein said generating means comprises:switchmeans interposed between two of said three leads for electricallyconnecting said one lead to the other lead.
 5. The apparatus of claim 4,wherein said switch means is an optically driven SCR switch.
 6. In a gaslaser havinga gas lasing medium; a gas discharge tube enclosing saidmedium; said tube having at least two electrodes; an optical resonatorstructure aligned with said discharge tube; and means for exciting saidmedium in said discharge tube, said means including:three leadsconnecting to a three-phase power source; a plurality of primary coils;said coils connected to said leads; a plurality of secondary coils, saidcoils supplying power to said electrodes; transformer means forincreasing the voltage from the power source through the primary coilsto the secondary coils the improvement comprising; means for changingthe magnetic flux flow pattern in said transformer means from symmetricflux pattern to an asymmetric flux pattern; whereby said symmetric fluxpattern causes said laser to operate in a continuous mode and saidasymmetric flux pattern causes said laser to operate in a pulsing mode.7. The laser of claim 6, wherein said changing means comprisesswitchmeans interposed between one of said three leads and one of said primarycoils for electrically disconnecting said lead to said coil.
 8. Thelaser of claim 7, wherein said switch means is an optically driven SCRswitch.
 9. The laser of claim 6, wherein said changing meanscomprisesswitch means interposed between two of said three leads forelectrically connecting said one lead to the other lead.
 10. The laserof claim 9, wherein said switch means is an optically driven SCR switch.